Antenna with short line tuning stub

ABSTRACT

In a system for providing lobing only when the system is switched to track operation and then only on receive and not on transmit, the normal track arm is replaced by a short tuning stub which is placed adjacent the output window of the standard trislot transmit-receive tube, so that the trislot reacts on the beam being received through the on-center feed to provide lobing action. A polarization sensitive grid having a plurality of parallel wires is located within the tuning stub. The stub is supported on bearings and is rotatable by means of a lever to switch the grid between the search mode position and the track mode position. An attenuation card is supported on a support plate within the tuning stub.

tlnited States Patent [191 Tellier et a1.

[451 Dec. 31, 1974 i ANTENNA WITH SHORT LINE TUNING STUB [75] Inventors:Jacob Tellier; Henry G. Burnett,

- both of Dallas, Tex.; Thomas S.

Lewis, Charlottesville, Va.

[22] Filed: Oct. 18, 1965 [21] App]. No.: 497,571

[52] U.S. Cl. 343/100 PE, 343/756 [51] Int. Cl. H04b 7/00 [58] Field ofSearch 343/1003, 100.5, 100,

12/1961 Wheeler 343/1003 l/l966 Matson 343/775 Primary ExaminerRichardA. Farley Assistant Examiner-T. M. Blum Attorney, Agent, or Firm-HarryA. Herbert, Jr.; Richard .1. Killoren 57] ABSTRACT In a system forproviding lobing only when the system is switched to track operation andthen only on receive and not on transmit, the normal track arm isreplaced by a short tuning stub which is placed adjacent the outputwindow of the standard trislot transmitreceive tube, so that the trislotreacts on the beam being received through the on-center feed to providelobing action. A polarization sensitive grid having a plurality ofparallel wires is located within the tuning stub. The stub is supportedon bearings and is rotatable by means of a lever to switch the gridbetween the search mode position and the track mode position. Anattenuation card is supported on a support plate within the tuning stub.

4 Claims, 10 Drawing Figures Pas Pat 4 PATENTED 1 7 SHEET 3 OF 3 s F w x/f g 2 w m5 v A 6 5% way Pv y (M umflf m mwwmli mw rfii| 1 ANTENNA WITHSHORT LINE TUNING STUB This invention relates to an improved Lobe-on-Receive-on-Track-Only antenna which will hereinafter be referred to as aLOROTO antenna.

One object of the invention is to provide a LOROTO antenna requiringfewer components than prior art structure.

Another object of the invention is to provide a LOROTO antenna whichincorporates a method for defeating circularly polarized jammers.

These and other objects will be more fully understood from the followingdetailed description taken with the drawing, wherein:

FIG. 1 is a partially schematic plan view of a prior LOROTO antenna;

FIG. 2 is a partially schematic plan view of a LOROTO antenna accordingto this invention;

F IG. 3 is an enlarged view, partially in section, of the modifiedantenna feed system of the device of FIG. 2;

FIG. 4 is atop view of the feed system of FIG. 3;

FIG. 5A is a schematic cross-sectional view of the short line unit ofthe device of FIG. 3 in the search mode;

FIG. 5B is an end view of the short line unit of FIG. 5A;

FIG. 5C shows the quadrative components of circular polarization asrelated to the position of the tuning stub in FIGS. 5A and SB;

FIG. 6A is a schematic cross-sectional view of the short line unit ofthe device of FIG. 3 in the track mode;

FIG. 6B is an end view of the short line unit of FIG. 6A; and,

FIG. 60 shows the quadrative components of circular polarization asrelated to the position of the tuning stub in FIGS. 6A and 68.

One form of prior art LOROTO antenna to which this invention applies isshown in FIG. 1. In these systerns lobing action takes place only duringtrack operation and not during search operation and then only onreceive-track. This antenna has a reflector 10, a center feed 12,transmit-receive-search arm 13, a receive track arm 14, and a pluralityof feed support rods, one.

of which is shown at 15. The center feed terminates in a Teflon mushroom16 and a serrated transmit splash plate 17, shown in greater detail inFIG. 3. A trislot pre- TR tube 18, is connected between the serratedreceive ring 19, shown in greater detail in FIG. 3, and the receivetrack arm 14. The pre-TR tube 18 has three energy receiving windows 28,two of which are shown, and an energy exit window 29 shown in FIG. 3.The choke ring 20 provides a primary pattern shaping element. A feedome'21 is provided around the antenna center feed. Rotation of the centerfeed is provided by means of a spinmotor 23.

It is evident in FIGS. 1 and 2 that energy from space collimated by thereflector and received at the primary radiator structure will be splitbetween the receive ring and the transmit splash plate in someproportion. The choke ring may be said to be aprimary pattern shapingelement. To effect efficient receive performance on the original lobingsystem, not shown, an ATR device was used in the transmit arm, as shownin FIG. 1, which was properly phased by a phase shift element 27 so asto present a short at the transmit splash plate entrance 17 so thatessentially all the energy received from space would enter the receivering, where it was modulated by the spinning trislot junction, and wouldpass back to the receiver through the receive track arm. On transmit,the high power would fire the pre-TR 18 so that the trislot junctionwould appear as a solid cylinder and no lobing would be effected. Thisbasic scheme was revised in the prior art device shown in FIG. .1accomplishing LOROTO by changing the ATR tube to an ATR-AATR device 22and adding the shorting switch 25 and phase shifter 26. In this deviceon receive search, the shorting switch is closed, the ATR tube 22 isswitched to AATR position and phase shifter 26 is used to present ashort at the trislot input in the unfired state. This shorts out thereceive ring so that the receive search energy passes through thetransmit arm 12. For track operation, the ATR-AATR device and theshorting switch are switched and the system again works as describedabove. Some of the difficulties with this design are the long linelengths to the shorting devices which make tuning supersensitive, theaperture blocking the receive track arm, and the multiplicity ofcomponents required.

The trislot junction may be used either as a transmission or as areactive device. In the prior art device, since the tracking energy isreceived through the trislot, the trislot may be said to be intransmission. An equally effective scheme can be devised by properlyterminating the trislot output with a stub so that the action of thetrislot reacts on the beam as being received through the on-center feed.

According to this invention, a mechanization of the reactive trislotconcept is shown in FIG. 2. Two stub lengths are required: (1) topresent a short at the trislot input for receive search operation; and,(2) to present an open circuit at the trislot input to effect modulationon receive track. The mechanism used to achieve the two stub-lengths isa circular waveguide which is polarization insensitive. A polarizationsensitive element is placed at a point to present a first short and theend of the circular stub is the second short plane. This polarizationsensitive element is a grid of parallel wires. When the wires areparallel to the impinging E vector, a short circuit is presented. If thegrid is rotated the wires act only as a septum and have no effect. Thusthe track arm 14, shorting switch 25, ATR-AATR device 22, and the phaseshifters 26 and 27 are made unnecessary.

As shown in greater detail in FIG. 3, the track arm is replaced by ashort tuning stub 30 placed adjacent the circular window 29 of thetrislot TR tube 18. The tuning stub 30 has a polarization sensitive grid31, with a plurality of parallel wires 32, located therein. A nattenuation card 33 is supported on a support plate 34, in anywell-known manner such as with an adhesive. The

.stub 30 is supported for rotation in bearings 37 and 38.

A stub driving lever 40 is driven by a rod 41 which passes throughhollow support rod 42 which is operated by push-pull solenoid device 43,shown in. block form in FIG. 2. The support plate 34 issecured to asupport spider 44 by a rectangular bolt 45 and nut 46 to preventrotation of the card as the stub is rotated. Other means to preventrotation of the card with the stub could also be provided. The remainderof the structure, except for the parts eliminated, is the same as in theprior art device of FIG. 1.

In the operation of the device in the receive search mode of operation,the tuning stub 30 is located to position the wires 32 parallel to theimpinging E vector and a short is presented so that the energy is notcoupled to the trislot tube, resulting in a nonlobing mode of operation.On track the solenoid drive 43 is operated to rotate the grid 31, 90 toposition the wires 32 perpendicular to the impinging E vector so that itis invisible to the properly polarized energy. The back wall 35 of thestub 30 is positioned to provide the proper coupling between the centerfeed and the trislot tube, resulting in a lobing mode on track. Theposition of the grid and back wall can be determined experimentally.

The polarization of a circularly polarized jammer may be thought of astwo components displaced by 90 as shown in FIGS. 5C and 6C.

With the grid in the track position, component (b) will be rejected (notcoupled to the trislot). Component (a) will be coupled to the trislot,but since it is not cross polarized in respect to the transmittedenergy, it will not result in a phase error at the reference generatorof the antenna.

With the grid in the search position, component (a) will be rejectedfrom the trislot. By means of the RF attenuator card 33, component (b)can be absorbed without affecting the required polarization.

There is thus provided a LOROTO antenna requiring fewer components thanprior art devices which thus simplifies some of the design difficulties.

Though a certain specific embodiment has been described, it is obviousthat numerous changes may be made without departing from the generalprinciple and scope of the invention.

We claim:

1. In an antenna, for providing lobing on receive on track only for aradio-frequency signalwith a predetermined polarization, having areflector; a center feed; means for supporting said center feed in frontof said reflector; a transmit splash plate on the end of said centerfeed; a serrated receive ring surrounding said transmit splash plate; atrislot TR tube mounted on said center feed in energy receiving relationto said receiving ring; said trislot transmit-receive tube having acircular window on the side thereof remote from said transmitter splashplate; means adjacent said circular window of said trislottransmit-receive tube, adapted to be switched between two predeterminedangular positions, for presenting a short at the trislot tube input tosaid radio-frequency signal in one position and for presenting an opencircuit at the trislot tube input, to said radio-frequency signal toeffect modulation of the receive signal by said trislot transmit-receivetube in the other position and means for selectively switching said lastnamed means between said two predetermined positions.

2. In an antenna, for providing lobing on receive on track only for aradio-frequency signal with a predetermined polarization, having areflector; a center feed; means for supporting said center feed in frontof said reflector; a transmit splash plate on the end of said centerfeed; a serrated receive ring surrounding said transmit splash plate; atrislot transmit-receive tube mounted on said center feed in energyreceiving relation to said receiving ring; said trislot transmit-receivetube having a circular window on the side thereof remote from saidtransmitter splash plate; a circular waveguide stub having an open endadjacent said circular window of said trislot transmit-receive tube anda closed end spaced a predetermined distance from said trislot tube topresent an open circuit at the trislot tube input, to saidradio-frequency signal, to effect modulation of the receive signal bysaid trislot transmit-receive tube; a grid, having a plurality ofparallel wires, within said waveguide stub and spaced from said trislottube by a predetermined distance; means for rotating said stub and saidgrid between two predetermined angular positions, to present a short atthe trislot tube input in one position of said grid and an open circuitat the trislot tube input to said radio frequency signal in the otherposition of said grid; and an attenuation means within said waveguidestub for attenuating undesired received signals.

3. In an antenna, for providing lobing on receive on track only for aradio-frequency signal with a predetermined polarization, having areflector; a center feed; means for supporting said center feed in frontof said reflector; a transmit splash plate on the end of said centerfeed; a serrated receive ring surrounding said transmit splash plate; atrislot transmit-receive tube mounted on said center feed in energyreceiving relation to said receiving ring; said trislot transmit-receivetube having a circular window on the side thereof remote from saidtransmitter splash plate; a circular waveguide stub having an open endadjacent said circular window of said trislot transmit-receive tube anda closed end spaced a predetermined distance from said trislot tube topresent an open circuit at the trislot tube input to saidradio-frequency signal to effect modulation of the receive signal bysaid trislot transmit-receive tube; a grid, having a plurality ofparallel wires, within said waveguide stub and spaced from said trislottube by a predetermined distance; means including a pushpull solenoiddrive for rotating said stub and said grid between two predeterminedangular positions, to present a short at the trislot tube input in oneposition of said grid and an open circuit at the trislot tube input tosaid radio-frequency signal in the other position of said grid; anattenuation means within said waveguide stub for attenuating undesiredreceived signals; and means for supporting said attenuation means in afixed angular position, as said waveguide stub is rotated.

4. In combination with an antenna, for providing lobing on receive ontrack only for a radio-frequency signal with a predeterminedpolarization, having: a reflector; a center feed; means for supportingsaid center feed in front of said reflector; a transmit splash plate onElfil f s id ent fe di tr ns n trre i 92m 291 nected to said centerfeed; a serrated receive ring surrounding said transmit splash plate; atrislot transmitreceive tube mounted on said center feed in energyreceiving relation to said receiving ring; said trislot transmit-receivetube having a circular window on the side thereof remote from saidtransmitter splash plate; a device for reacting on the beam beingreceived through said center feed, comprising: a circular waveguide stubhaving an open end adjacent said circular window of said trislottransmit-receive tube and a closed end spaced a predetermined distancefrom said trislot tube to present an open circuit at the trislot tubeinput to said radio-frequency signal to effect modulation of the receivesignal by said trislot transmit-receive tube; a grid, having a pluralityof parallel wires, within said waveguide stub and spaced from saidtrislot tube by a predetermined distance to present a short at thetrislot tube input; means for rotating said stub and said grid betweentwo predetermined angular positions, to present a short at the trislottube input in one position of said grid and an open circuit at thetrislot tube input to said radio-frequency signal in the other positionof said grid; an attenuation means within said waveguide stub forattenuating undesired received signals; and means for supporting saidattenuation means in a fixed angular position, as said waveguide stub isrotated.

UNITED STATES PATENT QFFICE CERTIFICATE OF CORRECTION PATENT NO. I3,858,213 DATED i 31 December 1974 INVENTOR( I Jacob Tellier et al It iscertified that error appears in the ab0ve-identitied patent and thatsaid Letters Patent are hereby corrected as shown below:

The following paragraph should appear on page 1, following the title.

RIGHTS OF THE GOVERNMENT The invention described herein may bemanufactured and used by or for the Government of the United States forall governmental purposes without the payment of any royalty.

' Signed and Scaled this I Sixteenth D y f November 1976 [SEAL] A ttest.

RUTH C. MASON C MARSHALL DANN Arresting Officer (nmmr'ssiuner nfParentsand Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPATENT NO. I 3,858,215 DATED I 31 December 1974 INVENTOR(S) JacobTellier et al It is certified that error appears in the ab0ve-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

The following paragraph should appear on page 1, following the title.

RIGHTS OF THE GOVERNMENT The invention described herein may bemanufactured and used by or for the Government of the United States forall governmental purposes without the payment of any royalty.

Signed and Sealed this Sixteenth D y f November 1976 [SEAL] Arrest;

RUTH C. M A SON C. MARSHALL DANN Alrestmg Officer Commissioner ufParentsand Trademarks

1. In an antenna, for providing lobing on receive on track only for aradio-frequency signal with a predetermined polarization, having areflector; a center feed; means for supporting said center feed in frontof said reflector; a transmit splash plate on the end of said centerfeed; a serrated receive ring surrounding said transmit splash plate; atrislot TR tube mounted on said center feed in energy receiving relationto said receiving ring; said trislot transmit-receive tube having acircular window on the side thereof remote from said transmitter splashplate; means adjacent said circular window of said trislottransmit-receive tube, adapted to be switched between two predeterminedangular positions, for presenting a short at the trislot tube input tosaid radio-frequency signal in one position and for presenting an opencircuit at the trislot tube input, to said radio-frequency signal toeffect modulation of the receive signal by said trislot transmit-receivetube in the other position and means for selectively switching said lastnamed means between said two predetermined positions.
 2. In an antenna,for providing lobing on receive on track only for a radio-frequencysignal with a predetermined polarization, having a reflector; a centerfeed; means for supporting said center feed in front of said reflector;a transmit splash plate on the end of said center feed; a serratedreceive ring surrounding said transmit splash plate; a trislottransmit-receive tube mounted on said center feed in energy receivingrelation to said receiving ring; said trislot transmit-receive tubehaving a circular window on the side thereof remote from saidtransmitter splash plate; a circular waveguide stub having an open endadjacent said circular window of said trislot transmit-receive tube anda closed end spaced a predetermined distance from said trislot tube topresent an open circuit at the trislot tube input, to saidradio-frequency signal, to effect modulation of the receive signal bysaid trislot transmit-receive tube; a grid, having a plurality ofparallel wires, within said waveguide stub and spaced from said trislottube by a preDetermined distance; means for rotating said stub and saidgrid between two predetermined angular positions, to present a short atthe trislot tube input in one position of said grid and an open circuitat the trislot tube input to said radio frequency signal in the otherposition of said grid; and an attenuation means within said waveguidestub for attenuating undesired received signals.
 3. In an antenna, forproviding lobing on receive on track only for a radio-frequency signalwith a predetermined polarization, having a reflector; a center feed;means for supporting said center feed in front of said reflector; atransmit splash plate on the end of said center feed; a serrated receivering surrounding said transmit splash plate; a trislot transmit-receivetube mounted on said center feed in energy receiving relation to saidreceiving ring; said trislot transmit-receive tube having a circularwindow on the side thereof remote from said transmitter splash plate; acircular waveguide stub having an open end adjacent said circular windowof said trislot transmit-receive tube and a closed end spaced apredetermined distance from said trislot tube to present an open circuitat the trislot tube input to said radio-frequency signal to effectmodulation of the receive signal by said trislot transmit-receive tube;a grid, having a plurality of parallel wires, within said waveguide stuband spaced from said trislot tube by a predetermined distance; meansincluding a push-pull solenoid drive for rotating said stub and saidgrid between two predetermined angular positions, to present a short atthe trislot tube input in one position of said grid and an open circuitat the trislot tube input to said radio-frequency signal in the otherposition of said grid; an attenuation means within said waveguide stubfor attenuating undesired received signals; and means for supportingsaid attenuation means in a fixed angular position, as said waveguidestub is rotated.
 4. In combination with an antenna, for providing lobingon receive on track only for a radio-frequency signal with apredetermined polarization, having: a reflector; a center feed; meansfor supporting said center feed in front of said reflector; a transmitsplash plate on the end of said center feed; a transmitreceive armconnected to said center feed; a serrated receive ring surrounding saidtransmit splash plate; a trislot transmit-receive tube mounted on saidcenter feed in energy receiving relation to said receiving ring; saidtrislot transmit-receive tube having a circular window on the sidethereof remote from said transmitter splash plate; a device for reactingon the beam being received through said center feed, comprising: acircular waveguide stub having an open end adjacent said circular windowof said trislot transmit-receive tube and a closed end spaced apredetermined distance from said trislot tube to present an open circuitat the trislot tube input to said radio-frequency signal to effectmodulation of the receive signal by said trislot transmit-receive tube;a grid, having a plurality of parallel wires, within said waveguide stuband spaced from said trislot tube by a predetermined distance to presenta short at the trislot tube input; means for rotating said stub and saidgrid between two predetermined angular positions, to present a short atthe trislot tube input in one position of said grid and an open circuitat the trislot tube input to said radio-frequency signal in the otherposition of said grid; an attenuation means within said waveguide stubfor attenuating undesired received signals; and means for supportingsaid attenuation means in a fixed angular position, as said waveguidestub is rotated.